Catheters are medical devices that can be inserted into a body cavity, duct, or vessel to treat diseases or perform a surgical procedure. Catheterization, for example, is performed in cardiovascular, urological, gastrointestinal, neurovascular, and ophthalmic applications. Catheters can allow drainage, administration of fluids or gases, access by surgical instruments, and perform wide variety of other tasks depending on the type of catheter. Catheters can, for instance, include energy emitting devices, such as laser and other radiation emitters, to ablate or cauterize tissue. In most uses, catheter is a thin, flexible tube (“soft” catheter) though catheters are available in varying levels of stiffness depending on the application.
Catheterization is normally performed in a series of steps. An introducer needle is first inserted into the body lumen followed by insertion of a guide wire through the introducer needle and into the lumen. The inserted introducer needle is removed, and an introducer sheath and/or dilator are introduced over the guide wire into the desired position to hold the body lumen open and allow insertion of tools, such as the catheter. The catheter can be introduced through the lumen of the introducer sheath using the wire as a guide.
In many applications, the rate of advancement and/or removal of catheters is important not only to patient safety but also to optimal usage of the catheter. Some catheters require a narrow range of advancement rates for effective performance. Laser catheters, for example, should be advanced at a rate of less than about 1 mm/second. Advancing too quickly can increase risk of injury (such as during superior vena cava during lead extraction), increase the forces acting at the laser sheath tip, and prevent the laser from properly ablating tissue (particularly with a smaller body lumen diameter with rapid catheter advancement). Advancing too slowly and lasing tissue too long can also provide poor results.